1 files changed, 75 insertions, 0 deletions
diff --git a/js/src/frontend/TDZCheckCache.cpp b/js/src/frontend/TDZCheckCache.cpp
new file mode 100644
index 0000000000..6cb4abfc50
--- /dev/null
+++ b/js/src/frontend/TDZCheckCache.cpp
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "frontend/TDZCheckCache.h"
+
+#include "frontend/BytecodeEmitter.h"
+
+using namespace js;
+using namespace js::frontend;
+
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+
+TDZCheckCache::TDZCheckCache(BytecodeEmitter* bce)
+    : Nestable<TDZCheckCache>(&bce->innermostTDZCheckCache),
+      cache_(bce->cx->frontendCollectionPool()) {}
+
+bool TDZCheckCache::ensureCache(BytecodeEmitter* bce) {
+  return cache_ || cache_.acquire(bce->cx);
+}
+
+Maybe<MaybeCheckTDZ> TDZCheckCache::needsTDZCheck(BytecodeEmitter* bce,
+                                                  const ParserAtom* name) {
+  if (!ensureCache(bce)) {
+    return Nothing();
+  }
+
+  CheckTDZMap::AddPtr p = cache_->lookupForAdd(name);
+  if (p) {
+    return Some(p->value().wrapped);
+  }
+
+  MaybeCheckTDZ rv = CheckTDZ;
+  for (TDZCheckCache* it = enclosing(); it; it = it->enclosing()) {
+    if (it->cache_) {
+      if (CheckTDZMap::Ptr p2 = it->cache_->lookup(name)) {
+        rv = p2->value();
+        break;
+      }
+    }
+  }
+
+  if (!cache_->add(p, name, rv)) {
+    ReportOutOfMemory(bce->cx);
+    return Nothing();
+  }
+
+  return Some(rv);
+}
+
+bool TDZCheckCache::noteTDZCheck(BytecodeEmitter* bce, const ParserAtom* name,
+                                 MaybeCheckTDZ check) {
+  if (!ensureCache(bce)) {
+    return false;
+  }
+
+  CheckTDZMap::AddPtr p = cache_->lookupForAdd(name);
+  if (p) {
+    MOZ_ASSERT(
+        !check,
+        "TDZ only needs to be checked once per binding per basic block.");
+    p->value() = check;
+  } else {
+    if (!cache_->add(p, name, check)) {
+      ReportOutOfMemory(bce->cx);
+      return false;
+    }
+  }
+
+  return true;
+}